In an ink jet device such as an ink jet printer that naturally drops an ink droplet while moving a carriage in a main scanning direction, a gap of an ink discharge port and a landing target object needs to be adjusted to an appropriate distance to land the ink droplet at an appropriate position. However, if an adjustment of an accuracy of smaller than or equal to 0.1 mm is required when adjusting the length of the gap, the visual adjustment using a scale, and the like becomes very difficult. Thus, an adjustment method in which the accuracy of smaller than or equal to 0.1 mm is required is proposed in Patent Literature 1 and Patent Literature 2.
Patent Literature 1 discloses a method of measuring a gap with a photosensor, and adjusting the length of the gap according to the measurement result. Patent Literature 2 discloses an examination method of an ink jet head of creating a calibration curve indicating a shift in a landing position and an interval with a gap, and detecting a position shift distance of an ink discharge port according to the calibration curve.